Field of the Disclosure
The present disclosure generally relates to a dart detector for cementing a tubular string into a wellbore.
Description of the Related Art
A wellbore is formed to access hydrocarbon bearing formations, such as crude oil and/or natural gas, by the use of drilling. Drilling is accomplished by utilizing a drill bit that is mounted on the end of a drill string. To drill within the wellbore to a predetermined depth, the drill string is often rotated by a top drive or rotary table on a surface platform or rig, and/or by a downhole motor mounted towards the lower end of the drill string. After drilling to a predetermined depth, the drill string and drill bit are removed and a casing string is lowered into the wellbore. An annulus is thus formed between the string of casing and the wellbore. The casing string is cemented into the wellbore by circulating cement slurry into the annulus. The combination of cement and casing strengthens the wellbore and facilitates the isolation of certain formations behind the casing for the production of hydrocarbons.
Typical prior art cementing plug containers utilize a mechanical lever actuated type plug release indicator to indicate the passage of the cementing plug from the cementing plug containers. In some instances, these prior art mechanical lever actuated type plug release indicators may indicate the passage of the cementing plug from the cementing plug container, although the cementing plug is still contained within the container. The failure to properly release the cementing plug from the cementing plug container can lead to the over-displacement of the cement slurry to insure an adequate amount of cement slurry has been pumped into the annulus.
Another type of cementing plug indicator utilizes a radioactive nail placed into the cementing plug. When the cementing plug having the radioactive nail lodged therein is no longer present in the cementing plug container, a Geiger counter will not react to the radiation emitted from the radioactive nail in the cementing plug thereby indicating that the plug is no longer in the cementing plug container. However, such nails may be difficult to obtain and store.